In vertebrate animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary, and are each mounted in an annulus comprising dense fibrous rings attached either directly or indirectly to the atrial and ventricular muscle fibers.
Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. Diseased heart valves may be categorized as either stenotic, wherein the valve does not open sufficiently to allow adequate forward flow of blood through the valve, and/or incompetent, wherein the valve does not close completely, causing excessive backward flow of blood through the valve when the valve is closed. Valve disease can be severely debilitating and even fatal if left untreated.
Various surgical techniques may be used to repair a diseased or damaged valve. In a valve replacement operation, the damaged leaflets are excised and the annulus sculpted to receive a replacement valve.
Another less drastic method for treating defective valves is through repair or reconstruction, which is typically used on minimally calcified valves. One repair technique that has been shown to be effective in treating incompetence is annuloplasty, in which the effective size of the valve annulus is contracted by attaching a prosthetic annuloplasty repair segment or ring to an interior wall of the heart around the valve annulus. The annuloplasty ring is designed to support the functional changes that occur during the cardiac cycle: maintaining coaptation and valve integrity to prevent reverse flow while permitting good hemodynamics during forward flow. The annuloplasty ring typically comprises an inner substrate of a metal such as stainless or titanium, or a flexible material such as silicone rubber or Dacron cordage, covered with a biocompatible fabric or cloth to allow the ring to be sutured to the heart tissue. Annuloplasty rings may be stiff or flexible, may be split or continuous, and may have a variety of shapes, including circular, D-shaped, C-shaped, or kidney-shaped. Examples are seen in U.S. Pat. Nos. 5,041,130, 5,104,407, 5,201,880, 5,258,021, 5,607,471 and, 6,187,040 B1. Most annuloplasty rings are formed in a plane, with some D-shaped rings being bowed along their anterior or straight side to conform to the annulus at that location.
The present application has particular relevance to the repair of tricuspid valve, which regulates blood flow between the right atrium (RA) and right ventricle (RV), although certain aspects may apply to repair of other of the heart valves.
The tricuspid valve 20 is seen in plan view in FIG. 1 and includes an annulus 22 and three leaflets 24a, 24b, 24c (septal, anterior, and posterior, respectively) extending inward into the flow orifice defined by the annulus. Chordae tendineae 26 connect the leaflets to papillary muscles located in the RV to control the movement of the leaflets. The tricuspid annulus 22 is an ovoid-shaped fibrous ring at the base of the valve that is less prominent than the mitral annulus, but slightly larger in circumference. The septal leaflet 24a is the site of attachment to the fibrous trigone, the fibrous “skeletal” structure within the heart. The triangle of Koch 30 and tendon of Todaro 32 provide anatomic landmarks during tricuspid valve repair procedures. The atrioventricular (AV) node 34 is a section of nodal tissue that delays cardiac impulses from the sinoatrial node to allow the atria to contract and empty their contents first, and relays cardiac impulses to the atrioventricular bundle. In a normal heart rhythm, the sinoatrial node generates an electrical impulse that travels through the right and left atrial muscles producing electrical changes which is represented on the electrocardiogram (ECG) by the p-wave. The electrical impulse then continues to travel through the specialized tissue of the AV node 34, which conducts electricity at a slower pace. This will create a pause (PR interval) before the ventricles are stimulated. Of course, surgeons must avoid placing sutures too close to or within the AV node 34. C-rings are good choices for tricuspid valve repairs because they allow surgeons to position the break in the ring adjacent the AV node 34, thus avoiding the need for suturing at that location.
Despite numerous designs presently available or proposed in the past, there is a need for a tricuspid ring that more closely conforms to the actual shape of the tricuspid annulus.